CN110790702A - Method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation - Google Patents
Method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation Download PDFInfo
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- CN110790702A CN110790702A CN201911094440.7A CN201911094440A CN110790702A CN 110790702 A CN110790702 A CN 110790702A CN 201911094440 A CN201911094440 A CN 201911094440A CN 110790702 A CN110790702 A CN 110790702A
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- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D213/78—Carbon atoms having three bonds to hetero atoms, with at the most one bond to halogen, e.g. ester or nitrile radicals
- C07D213/84—Nitriles
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Abstract
The invention provides a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation, which comprises the following steps: (1) chemical recrystallization: mixing dichloromethane and ethanol according to a volume ratio to obtain a mixed solvent, heating to 50-55 ℃, and adding a crude product of 4-cyanopyridine while stirring; after complete dissolution, cooling to 30-35 ℃, adding petroleum ether, and cooling to room temperature; then standing for 6-12h at 4-5 ℃, and filtering, washing and drying the precipitated solid; (2) physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 82-86 ℃, and completely melting the substance; then slowly cooling to 55-57 ℃, and crystallizing; discharging the melt without forming the crystal, filtering, washing and drying the obtained crystal to obtain the 4-cyanopyridine with the purity of more than 99 percent. The method can obtain the high-purity 4-cyanopyridine only by two steps of chemical recrystallization and physical separation, and has high total extraction rate.
Description
Technical Field
The invention relates to the technical field of 4-cyanopyridine production, in particular to a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation.
Background
The 4-cyanopyridine can be used as an intermediate for producing compound pyridine derivatives in the agricultural and pharmaceutical industries, and is mainly used for producing isonicotinamide, isonicotinic acid and ramification. 4-cyanopyridine is an important medicine and has high requirements on the purity of the medicine. In order to obtain 4-cyanopyridine with high purity, purification and purification are required.
4-methylpyridine is the only raw material for preparing 4-cyanopyridine, but 4-methylpyridine with purity of more than 97% is expensive, so 4-cyanopyridine is prepared by a methylamine reaction by using 4-methylpyridine containing about 10% of 3-methylpyridine as a raw material in production. However, the boiling points of 3-methylpyridine and 4-methylpyridine only differ by 0.7 ℃, and the separation is difficult, so that the obtained mixture of 4-cyanopyridine and 3-cyanopyridine is separated from the mixed system of 3-cyanopyridine and 4-cyanopyridine by adopting a vacuum rectification method for industrial separation so as to improve the economic benefit. The separation effect of 4-cyanopyridine in industrial production is poor and satisfactory, and the operation cost is high.
Disclosure of Invention
The invention aims to provide a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation, which can obtain high-purity 4-cyanopyridine by only two steps of chemical recrystallization and physical separation and has high total extraction rate.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation comprises the following steps:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to the volume ratio of 6-15: 1, mixing to obtain a mixed solvent, heating the mixed solvent to 50-55 ℃, and then adding a crude product of 4-cyanopyridine while stirring; after the crude product of the 4-cyanopyridine is completely dissolved, placing the mixture at room temperature, cooling the mixture to 30-35 ℃, adding petroleum ether with the volume of 10-20% of that of dichloromethane, and cooling the mixture to room temperature; then standing for 6-12h at 4-5 ℃, and filtering, washing and drying the precipitated solid;
(2) physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 82-86 ℃, and completely melting the substance; then slowly cooling to 55-57 ℃, and then crystallizing; discharging the melt without forming the crystal, filtering, washing and drying the obtained crystal to obtain the 4-cyanopyridine with the purity of more than 99 percent.
Preferably, in the step (1), the crude 4-cyanopyridine is a mixture of 4-cyanopyridine and 3-cyanopyridine, wherein the mass percentage of the 4-cyanopyridine is 86-95.5%.
Preferably, in the step (1), the mass-to-volume ratio of the crude 4-cyanopyridine product to the mixed solvent is 1: 0.8-1.5 g/mL.
Preferably, in step (1), petroleum ether is added in an amount of 15 to 18% by volume of methylene chloride.
Preferably, the crystallization time in step (2) is 2-3 h.
Preferably, in the step (2), the temperature is slowly reduced to 55-57 ℃ at the cooling speed of 2-3 ℃/5 min.
Preferably, in both steps (1) and (2), washing is carried out with dichloromethane.
The invention has the beneficial effects that:
the method comprises the steps of firstly heating dichloromethane-ethanol to dissolve a 4-cyanopyridine crude product, dissolving 4-cyanopyridine and 3-cyanopyridine in the 4-cyanopyridine crude product, wherein most of 3-cyanopyridine is dissolved in a solvent in the process of cooling, and 4-cyanopyridine is largely crystallized, particularly, when the temperature is cooled to 30-35 ℃, a proper amount of petroleum ether is added, so that the crystallization of the 4-cyanopyridine can be further promoted, the purity of the obtained 4-cyanopyridine is increased, and the 4-cyanopyridine with the purity of more than 97.5 percent can be obtained after the operation of the step (1).
And then, physically separating the obtained 4-cyanopyridine with the purity of more than 97.5 percent, and mainly carrying out further purification according to the difference of melting points of the 4-cyanopyridine and the 3-cyanopyridine, wherein the 3-cyanopyridine with the low melting point hardly crystallizes at 55-57 ℃, the 4-cyanopyridine crystallizes completely, and then washing by using dichloromethane, so that the purity of the obtained 4-cyanopyridine is more than 99.0 percent, and the total extraction rate is high and can reach more than 92 percent.
Meanwhile, the method has simple process, only needs two steps of chemical recrystallization and physical separation, does not need repeated operation in the middle, has simpler operation, and is suitable for industrial production.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation comprises the following steps:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to a volume ratio of 10: 1 to obtain a mixed solvent, heating the mixed solvent to 52 ℃, and then adding a crude 4-cyanopyridine product while stirring, wherein the mass-to-volume ratio of the crude 4-cyanopyridine product to the mixed solvent is 1: 1 g/mL; wherein the crude product of the 4-cyanopyridine is a mixture of the 4-cyanopyridine and the 3-cyanopyridine, and the mass percentage of the 4-cyanopyridine is 91.3 percent.
After the crude product of the 4-cyanopyridine is completely dissolved, placing the mixture at room temperature, cooling the mixture to 30 ℃, adding petroleum ether with the volume of 15 percent of dichloromethane, and cooling the mixture to room temperature; then, the mixture was left at 4 ℃ for 10 hours, and the precipitated solid was filtered, washed with dichloromethane, and dried.
(2) Physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 85 ℃, and completely melting the substance; then slowly cooling to 55.5 ℃ at the cooling speed of 2.5 ℃/5min, and then crystallizing for 2.5 h; discharging the melt without forming the crystal, filtering the obtained crystal, washing the obtained crystal by dichloromethane, and drying to obtain the 4-cyanopyridine with the purity of more than 99 percent.
The detection proves that the purity of the obtained 4-cyanopyridine product is 99.4 percent, and the total extraction rate of the product is 95.8 percent.
Example 2:
a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation comprises the following steps:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to a volume ratio of 15: 1 to obtain a mixed solvent, heating the mixed solvent to 55 ℃, and then adding a crude 4-cyanopyridine product while stirring, wherein the mass-to-volume ratio of the crude 4-cyanopyridine product to the mixed solvent is 1: 1.2 g/mL; wherein the crude product of the 4-cyanopyridine is a mixture of the 4-cyanopyridine and the 3-cyanopyridine, and the mass percentage of the 4-cyanopyridine is 95.5 percent.
After the crude product of the 4-cyanopyridine is completely dissolved, placing the crude product at room temperature, cooling the crude product to 35 ℃, adding petroleum ether with the volume of 18 percent of dichloromethane, and cooling the crude product to room temperature; then, the mixture was left at 4 to 5 ℃ for 8 hours, and the precipitated solid was filtered, washed with dichloromethane, and dried.
(2) Physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 82 ℃, and completely melting the substance; then slowly cooling to 55 ℃ at the cooling speed of 2 ℃/5min, and then crystallizing for 3 h; discharging the melt without forming the crystal, filtering the obtained crystal, washing the obtained crystal by dichloromethane, and drying to obtain the 4-cyanopyridine with the purity of more than 99 percent.
The detection shows that the purity of the obtained 4-cyanopyridine finished product is 99.6 percent, and the total extraction rate of the product is 93.7 percent.
Example 3:
a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation comprises the following steps:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to a volume ratio of 6: 1 to obtain a mixed solvent, heating the mixed solvent to 50-55 ℃, and then adding a crude 4-cyanopyridine product while stirring, wherein the mass-volume ratio of the crude 4-cyanopyridine product to the mixed solvent is 1: 0.8 g/mL; wherein the crude 4-cyanopyridine is a mixture of 4-cyanopyridine and 3-cyanopyridine, and the mass percentage of the 4-cyanopyridine is 86%.
After the crude product of the 4-cyanopyridine is completely dissolved, placing the mixture at room temperature, cooling the mixture to 30 ℃, adding petroleum ether with the volume of 20 percent of dichloromethane, and cooling the mixture to room temperature; then, the mixture was left at 5 ℃ for 12 hours, and the precipitated solid was filtered, washed with dichloromethane, and dried.
(2) Physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 83.5 ℃, and completely melting the substance; then slowly cooling to 55 ℃ at the cooling speed of 2.5 ℃/5min, and then crystallizing for 2.5 h; discharging the melt without forming the crystal, filtering the obtained crystal, washing the obtained crystal by dichloromethane, and drying to obtain the 4-cyanopyridine with the purity of more than 99 percent.
The detection shows that the purity of the obtained 4-cyanopyridine finished product is 99.2 percent, and the total extraction rate of the product is 94.3 percent.
Example 4:
a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation comprises the following steps:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to a volume ratio of 9: 1 to obtain a mixed solvent, heating the mixed solvent to 52 ℃, and then adding a crude 4-cyanopyridine product while stirring, wherein the mass-to-volume ratio of the crude 4-cyanopyridine product to the mixed solvent is 1: 1.5 g/mL; wherein the crude product of the 4-cyanopyridine is a mixture of the 4-cyanopyridine and the 3-cyanopyridine, and the mass percentage of the 4-cyanopyridine is 89.2 percent.
After the crude product of the 4-cyanopyridine is completely dissolved, placing the crude product at room temperature, cooling the crude product to 35 ℃, adding petroleum ether with the volume of 20 percent of dichloromethane, and cooling the crude product to room temperature; then, the mixture was left at 4 ℃ for 10 hours, and the precipitated solid was filtered, washed with dichloromethane, and dried.
(2) Physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 86 ℃, and completely melting the substance; then slowly cooling to 55 ℃ at a cooling speed of 3 ℃/5min, and then crystallizing for 2 h; discharging the melt without forming the crystal, filtering the obtained crystal, washing the obtained crystal by dichloromethane, and drying to obtain the 4-cyanopyridine with the purity of more than 99 percent.
The detection shows that the purity of the obtained 4-cyanopyridine finished product is 99.1 percent, and the total extraction rate of the product is 93.4 percent.
Example 5:
a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation comprises the following steps:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to a volume ratio of 9: 1 to obtain a mixed solvent, heating the mixed solvent to 50 ℃, and then adding a crude 4-cyanopyridine product while stirring, wherein the mass-to-volume ratio of the crude 4-cyanopyridine product to the mixed solvent is 1: 0.8 g/mL; wherein the crude product of the 4-cyanopyridine is a mixture of the 4-cyanopyridine and the 3-cyanopyridine, and the mass percentage of the 4-cyanopyridine is 95.5 percent.
After the crude product of the 4-cyanopyridine is completely dissolved, placing the mixture at room temperature, cooling the mixture to 30 ℃, adding petroleum ether with the volume of 10 percent of that of dichloromethane, and cooling the mixture to room temperature; then, the mixture was left at 5 ℃ for 6 hours, and the precipitated solid was filtered, washed with dichloromethane, and dried.
(2) Physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 82 ℃, and completely melting the substance; then slowly cooling to 57 ℃ at the cooling speed of 2 ℃/5min, and then crystallizing for 3 h; discharging the melt without forming the crystal, filtering the obtained crystal, washing the obtained crystal by dichloromethane, and drying to obtain the 4-cyanopyridine with the purity of more than 99 percent.
The detection shows that the purity of the obtained 4-cyanopyridine finished product is 99.5 percent, and the total extraction rate of the product is 92.7 percent.
Example 6:
a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation comprises the following steps:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to a volume ratio of 13: 1 to obtain a mixed solvent, heating the mixed solvent to 55 ℃, and then adding a crude 4-cyanopyridine product while stirring, wherein the mass-to-volume ratio of the crude 4-cyanopyridine product to the mixed solvent is 1: 1.3 g/mL; wherein the crude product of the 4-cyanopyridine is a mixture of the 4-cyanopyridine and the 3-cyanopyridine, and the mass percentage of the 4-cyanopyridine is 91.3 percent.
After the crude product of the 4-cyanopyridine is completely dissolved, placing the crude product at room temperature, cooling the crude product to 35 ℃, adding petroleum ether with the volume of 15 percent of dichloromethane, and cooling the crude product to room temperature; then, the mixture was left at 5 ℃ for 8 hours, and the precipitated solid was filtered, washed with dichloromethane, and dried.
(2) Physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 85 ℃, and completely melting the substance; then slowly cooling to 55-57 ℃ at the cooling speed of 2.5 ℃/5min, and then crystallizing for 2.5 h; discharging the melt without forming the crystal, filtering the obtained crystal, washing the obtained crystal by dichloromethane, and drying to obtain the 4-cyanopyridine with the purity of more than 99 percent.
The detection shows that the purity of the obtained 4-cyanopyridine finished product is 99.3 percent, and the total extraction rate of the product is 95.1 percent.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. The method for purifying the 4-cyanopyridine by combining chemical recrystallization and physical separation is characterized by comprising the following steps of:
(1) chemical recrystallization: mixing dichloromethane and ethanol according to the volume ratio of 6-15: 1, mixing to obtain a mixed solvent, heating the mixed solvent to 50-55 ℃, and then adding a crude product of 4-cyanopyridine while stirring; after the crude product of the 4-cyanopyridine is completely dissolved, placing the mixture at room temperature, cooling the mixture to 30-35 ℃, adding petroleum ether with the volume of 10-20% of that of dichloromethane, and cooling the mixture to room temperature; then standing for 6-12h at 4-5 ℃, and filtering, washing and drying the precipitated solid;
(2) physical separation: putting the substance obtained in the step (1) into a reactor, controlling the temperature of the reactor to be 82-86 ℃, and completely melting the substance; then slowly cooling to 55-57 ℃, and then crystallizing; discharging the melt without forming the crystal, filtering, washing and drying the obtained crystal to obtain the 4-cyanopyridine with the purity of more than 99 percent.
2. The method for purifying 4-cyanopyridine by the combination of chemical recrystallization and physical separation as claimed in claim 1, wherein in step (1), the crude 4-cyanopyridine is a mixture of 4-cyanopyridine and 3-cyanopyridine, wherein the mass percentage of 4-cyanopyridine is 86-95.5%.
3. The method for purifying 4-cyanopyridine by the combination of chemical recrystallization and physical separation as claimed in claim 1, wherein in step (1), the ratio of the crude 4-cyanopyridine to the mixed solvent is 1: 0.8-1.5 g/mL.
4. The method for purifying 4-cyanopyridine by the combination of chemical recrystallization and physical separation as claimed in claim 1, wherein the petroleum ether is added in an amount of 15-18% by volume based on the dichloromethane in step (1).
5. The method for purifying 4-cyanopyridine by the combination of chemical recrystallization and physical separation as described in claim 1, wherein the crystallization time in the step (2) is 2-3 hours.
6. The method for purifying 4-cyanopyridine by the combination of chemical recrystallization and physical separation as claimed in claim 1, wherein in the step (2), the temperature is slowly decreased to 55-57 ℃ at a rate of 2-3 ℃/5 min.
7. The method for purifying 4-cyanopyridine by the combination of chemical recrystallization and physical separation as claimed in claim 1, wherein in steps (1) and (2), washing with dichloromethane is carried out.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2021017649A1 (en) * | 2019-08-01 | 2021-02-04 | 安徽瑞邦生物科技有限公司 | Method for purifying 4-cyanopyridine by means of melting and crystallizing |
| CN113429343A (en) * | 2021-07-28 | 2021-09-24 | 安徽瑞邦生物科技有限公司 | Method for purifying 4-cyanopyridine by using static crystallization |
| CN114539143A (en) * | 2022-01-28 | 2022-05-27 | 安徽瑞邦生物科技有限公司 | Purification method of 4-cyanopyridine |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106478498A (en) * | 2016-09-23 | 2017-03-08 | 哈尔滨理工大学 | Using chemical recrystallization and physical separation combine purification 4 cyanopyridines method |
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- 2019-11-11 CN CN201911094440.7A patent/CN110790702A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106478498A (en) * | 2016-09-23 | 2017-03-08 | 哈尔滨理工大学 | Using chemical recrystallization and physical separation combine purification 4 cyanopyridines method |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2021017649A1 (en) * | 2019-08-01 | 2021-02-04 | 安徽瑞邦生物科技有限公司 | Method for purifying 4-cyanopyridine by means of melting and crystallizing |
| CN113429343A (en) * | 2021-07-28 | 2021-09-24 | 安徽瑞邦生物科技有限公司 | Method for purifying 4-cyanopyridine by using static crystallization |
| CN114539143A (en) * | 2022-01-28 | 2022-05-27 | 安徽瑞邦生物科技有限公司 | Purification method of 4-cyanopyridine |
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